Polychlorinated biphenyls (Aroclor 1221, 1232, 1242, 1248, 1254, 1260, 1262, and 1268), polychlorinated terphenyls (Aroclor 5460), a mixture of polychlorinated biphenyls and terphenyls (Aroclor 4465) and polybrominated biphenyls (BP-6) were administered in a single dose, 100 mg/kg body weight injected orally, to mature male and female Japanese quail. Two hr after Aroclor treatment, pentobarbital sleeping times were prolonged (2 to 3 times control) in both male and female quail. Twenty-four hr after treatment, sleeping times were similar to those of controls. However, 48 hr after treatment with Aroclor 1248 through Arolcor 5460 and with BP-6, sleeping times of males were only 1/2 those of controls, whereas after treatment with Aroclor 1221, 1232 and 1242, sleeping times were similar to those of controls. The reduction in sleeping times of male quail 48 hr after administration of PCBs was correlated with the percentage of chlorine in the PCB with greater reductions in male than female quail. The response after three days ad libitum feeding of 300 ppm of each substance was the same as the response 48 hr after a single oral injection. Although very few birds died from the toxicity of the Aroclors and BP-6, mortality was greatly increased during anesthesia when the pentobarbital was administered two hr after single oral dosing.